Intravascular interventional procedures for providing an artificial embolism are desirable in some patients for controlling internal bleeding, preventing blood supply to tumors, or relieving pressure in the vessel wall near an aneurysm. Several approaches are known for providing an artificial embolism, including the use of an inflatable, detachable balloon or the injection of a coagulative substance. Another approach utilizes an occlusive wire coil and delivery system for positioning the coil at a desirable site in a blood vessel.
One wire coil and delivery system includes a flexible, coiled wire that when released from the distal end of a delivery catheter assumes a randomly coiled, space-filling mass. The wire is released from the catheter by a pusher catheter with a closed distal end for engaging the proximal end of the coil. A problem with this system is that the wire coil is just pushed out the distal end of the delivery catheter toward the target embolism site and then assumes a folded, convoluted configuration. This folded, convoluted configuration is obtained with the use of an occlusion wire that possesses memory which returns the wire from a stretched to a relaxed convoluted condition. One problem with this convoluted configuration coil is that precise positioning of the coil at the occlusion site is difficult to obtain. This is mainly due to the coiled configuration of the wire in which the distal end of the convoluted wire engages the wall of the vessel and longitudinally displaces the delivery catheter. As a result, the delivery catheter and occlusion coil are proximally displaced from the desired occlusion site. Such longitudinal displacement can readily prevent an aneurysm from being occluded. Furthermore, the displaced convoluted coil, which is to be positioned in, for example, an aneurysm, then proceeds downstream and causes an occlusion at an undesired site. This can cause additional pressure to be applied to the already weakened wall of the aneurysm.
Another problem with this convoluted coil is ensuring that sufficient mass is positioned across the cross-sectional area of the vessel lumen to sufficiently restrict blood flow.